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Author Topic:   13-Foot: Anti-ventilation Plate Foil Appendage
Easy E posted 12-10-2000 09:12 PM ET (US)   Profile for Easy E  
Hi. A few months ago I re-powered my 13-foot Boston Whaler boat with a 35-HP Johnson that has power trim and tilt. As my first modification I installed a Powertech 15-inch-pitch SS cupped prop. I know would like to get a hydrofoil so I can fully utilize my power trim. How would [adding an anti-ventilation plate foil appendage] affect my handling and speed? I am currently getting 40-MPH compared to 35-MPH with the factory four-blade propeller. With my current setup [I am] getting GREAT fuel economy and [I] hope to be getting better with my new hydrofoil. Give me suggestions [about which anti-ventilation plate foil appendage to install]. Thanks in advance.

P.S.~I see [the brand Doel-Fin mentioned on this] web site. Is [the Doel-Fin brand] the way to go?

Clark Roberts posted 12-11-2000 07:01 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Easy, in my opinion: Doel-Fin
Whaletosh posted 12-11-2000 09:09 AM ET (US)     Profile for Whaletosh    
Trailer Boat Magazine and Bass and Walleye Boats (sister publications) conducted two sets of tests on hydrofoils. In both tests the SE Sport 300 sold by Cabelas and Bass Pro was the best for retaining top end speed, and was in the top of the pack for acceleration.

I have used this foil on 3 of 6 six boats that I have had, and the results were very good.

Some boats don't react well to a foil, my 2000 13 Sport didn't. You can always try one and fill the holes in the motor with Marine Tek if needed.

tbyrne posted 12-11-2000 06:27 PM ET (US)     Profile for tbyrne    
Whaletosh, I'm interested in your thoughts as to why the foil didn't go so well on your 2000 Sport 13. I have the same boat with the 25hp 4-stroke & can't decide whether the foil helps or hurts. I do know it gives me more trim range ant the cost of some top end. Beyond that, the jury is still out.
Hoop posted 12-11-2000 07:29 PM ET (US)     Profile for Hoop  Send Email to Hoop     
Whaletosh, What issue of "Trailerboats Magazine" had the test? I've got 2 or 3 years worth in my files.


Easy E posted 12-13-2000 03:50 AM ET (US)     Profile for Easy E    
OK. Now [I am] getting the idea that a [an anti-ventilation plate foil appendage] can actualy slow me down and give me better handling. I thought it would give me the same or better speed while giving me better handling. Which on is it? I was also lookling in to a Stingray-brand with torque stabilizers,. Has any one tried this? I'm probably going to get the SE Sport 300 if i don't find anything better. Thanks
Clark Roberts posted 12-13-2000 07:40 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Easy, there are two types of fins, . hydro-foils, which act like airfoils and create lift, and hydro-spoilers,which create drag. The Doel-Fin is a hydro-foil and creates lift aft. If motor is at correct height will ride at surface at WOT and will not cut speed (may increase speed due to providing extra trim-up range and thus less wetted surface on hull). The Stingray is a hydro-spoiler and will cut top speed! It is effective on stern heavy boats (like I/O's) and can provide a better hole shot. The above may be a gross analogy but should explain the differences. If a foil has a turned down trailing edge, it is a spoiler. I have hands-on experience with Doel-Fin, SST (a Doel-Fin clone), Stingray, and AttWood. I have Doel-Fins on two 13's, a 17, a 15, and a 21. So you can see my mind's made up--heh, heh.. Happy Whalin'... Clark.. Spruce Creek Navy
RWM posted 12-13-2000 12:43 PM ET (US)     Profile for RWM  Send Email to RWM     
Clark--Makes sense to me. I'm putting an Evinrude 70 HP 4-stroke on my 1979 Montaulk this spring. I'll be operating in fairly rough conditions (Cape Cod and Buzzards Bay). I'll have the battery in the rear and up to 24 gallons of gas, and I'll be stern heavy. I don't much care about maximum speed, but do want to plane quickly and keep the boat on plane at lower speeds.

Therefore, I want a Stingray-brand for my application. Agree? Bob M.

Whaletosh posted 12-13-2000 04:33 PM ET (US)     Profile for Whaletosh    

I lost top end, the boat was actually more prone to porpoising, and harder to plane. I have never had this happen with the Sport SE. Maybe others will work better.


I don't know when the test was done, maybe 4 or 5 years ago. I never read the test in Bass and Walleye Boats. These devices haven't changed in several years so I bet the results would be the same.

In general deep Vs will benifit the most from planing aids, flatter bottom boats the least. Top speed is usually worse but not much. Fuel mileage, planing time, and porposing are better. That is what generally happens, sometimes the results are not good; as was the case with my 13' Sport.

Easy E posted 12-13-2000 05:25 PM ET (US)     Profile for Easy E    
I think im gonna go with the Doel-Fin. Basically because it seems to me that its slimmer and has less drag(and because i've been told that Clark Roberts is one of the few "Whaler Gods" on this site and he uses it).The other hydrofoils has small skegs and keels thingies that i like but if its means less miles per gallon then forget it.Im not planning on making sharp turn while going 40mph anyway.So thanks people! Easy E...AKA Young Man And The
andygere posted 12-19-2000 01:32 AM ET (US)     Profile for andygere  Send Email to andygere     
I've got a Whale Tale on my 85 Johnson/Montauk (seems appropriate). I can't say how it compares to other brands in terms of performance, but it's made of aluminum and makes a handy step for climbing into the boat over the transom. I don't even bother to bring the clumsy swim ladder anymore.
MikeC posted 12-21-2000 07:39 AM ET (US)     Profile for MikeC  Send Email to MikeC     
Has anybody tried the aluminum tails amde by Bobs MAchine shop?I have used them on my drag boat nd my pleasure boat and the are real nice and they cost about They call it the broad tail stablizer plate
Mark Gallagher posted 12-24-2000 01:39 PM ET (US)     Profile for Mark Gallagher  Send Email to Mark Gallagher     
I am going to get a hydrofoil this season, it appears the benefits are many.

Clark, I was going to get the Doel-fin per your recommendations but I looked at the unit from, per Mikes comment - go to links on right side of their page, then click on porta -brackets and scroll down to see their looks good - Clark what do you think? It looks like you would remove the factory trim tab on the lower unit...I looks like a nice unit and I like the benefits they claim!!!!
Comments? Thoughts? BTW, I'm putting it on a Johnson 115 on a 17 Dauntless.....

MikeC posted 12-24-2000 04:11 PM ET (US)     Profile for MikeC  Send Email to MikeC     
You can leave the trim tab alone,there is a hole cut out for it on the bottom of the plate.The entire plate fastens with 4 stainless bolts with nylon lock nuts.Its real easy to install too.If you dont have hydraulic steering you can send them your gearcase and they weld a torque tab to your skeg and it really helps with the steering torque.It looks factory when its done.
Clark Roberts posted 12-25-2000 09:34 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Mark, I've heard nothing but praise for the Bob's aluminum fin. Haven't used one myself so can't testify! Am considering installing one on my buddy's 22 Revenge WT/WD with 2001 Merc Optimax 225. Bob's makes very good, high quality products... Clark
Easy E posted 01-02-2001 04:29 PM ET (US)     Profile for Easy E    
My Doel-Fin came in yesterday! I couldn't wait to try them out so this morning (5:00am) I installed them according to instructions--which wasnt hard or time consuming (about 30mins)--so 2 hours later [I] launched the boat. First thing [I] notice as [I] took off was how much easier it was to plane off. As [I] reached top speed [I] tilted the engine up and the boat responded much faster. When [I] reached top end speed with minimal hull in water [I] also notice the slight bow hop that [I] had before was gone. Then to boot my top speed which was a in between 39- to 40-MPH was now a solid 42-MPH! I didn't notice any thing significant with the steering but [I will} probably will when [I] start pulling skier and tubes. So all in all what [I] noticed with my Doel-Fin is my boat is now:

--faster to plane

--smoother ride

--faster trim response

--stopped slight bow hop

--gained 2.5-MPH AND better fuel economy.

I am very happy with my small investment. I never thought [I] can get 42-MPH from a 35 on a 13. Perhaps this weedend [I will] do some further testing with passengers, skiers, tubes etc. Well [I] think [I am] going to flush the engine out, then put her to bed.--Easy E

madsportster posted 10-20-2006 07:38 AM ET (US)     Profile for madsportster  Send Email to madsportster     
I have a 16-foot Yalta Craft with a 135-HP V6 Mercury Black Max Ouboard. Motor is quite heavy and affected the handling dynamics of the boat. Had to reach about 40-kilometers per hour to plane and slowing down was a bit daunting as well, when the bow would raise ight up giving the sensation of the stern going down. One of my mates told me about hydrofoils and I was dubious at first thinking they would only make marginal difference.

Fitted a SST Hydrofoil for $50-AUD and what a difference it has made.

The boat planes a lot sooner and now has great boat handling dynamics. Planes heaps faster (almost immediately) and feels so much light when travelling.

Spoke with a local Water Police Officer today, incidently the first day I tried the hydrofoil. He has one on a Haines Hunter with 115hp. He asked what I thought and said he swears by them.

Proof is in the tasting and the hydrofoil has certainly work very well in my situation.

jimh posted 10-21-2006 09:28 PM ET (US)     Profile for jimh  Send Email to jimh     
In case you decide to remove the foil appendage from your anti-ventilation plate, here is how to fill the holes left behind:

jimh posted 10-21-2006 09:32 PM ET (US)     Profile for jimh  Send Email to jimh     
Clark--If you or your friend install a foil appendage on the 225-HP motor on the REVENGE 22 W-T WD, please let us know how it affects the boat's performance. I would be very interested to hear of the outcome of that installation.
The Judge posted 10-23-2006 02:08 PM ET (US)     Profile for The Judge  Send Email to The Judge     
I am on the fence with adding one to my 13' but I have had good luck with them on other boats but NEVER on a 17'. The only advantage I saw on a 17 was I couldplane about 3mph slower...who cares. I do hate the porpoising on my 13 which I can alleviate by trimming in but then I slow down and get wet easier.....decisions!

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